In wideband amplifiers, it is desirable to maintain a constant gain-versus-frequency characteristic over the entire frequency spectrum. However, because of inherent physical limitations of semiconductor devices which may result in nonlinear distortion, thermal distortion, frequency distortion, or phase-shift distortion, amplifier fidelity is difficult to maintain over a wide range of frequencies without relying upon various frequency-compensation and transient-response-peaking techniques.
Wideband differential amplifiers such as those utilized in the vertical amplifier channels of oscilloscopes exhibit a large gain at the lower frequencies and a reduced gain at the higher frequencies. Heretofore, the approach to providing a constant gain over the entire amplifier bandwidth has been to boost the high-frequency gain by adding resistive-capacitive networks between the emitters of the differentially-coupled transistors of the amplifier. However, at very high frequencies, for example, above 500 megahertz, the inductive properties of the lead wires of the amplifier components become an undesirable factor in determining the frequency response. The circuit designer is thus faced with the dichotomous dilemma of reducing lead length and adding components to effect the required high-frequency boost.